1. Field of the Invention
The present invention relates to a diffusing adhesive layer excellent in balance between light transmittance and diffusing characteristic and adapted for formation of a liquid-crystal display device excellent in visibility such as brightness, and an optical member using the diffusing adhesive layer.
The present application is based on Japanese Patent Applications No. Hei. 11-159663 and 159664, which are incorporated herein by reference.
2. Description of the Related Art
Heretofore known was a light diffusion type adhesive layer which was configured to contain particles having refractive indices different from one another to thereby have light diffusing characteristic so that a viewing angle for liquid-crystal display could be enlarged. However, if the diffusing characteristic was improved to attain the enlargement of the viewing angle while self-adhesive applicability excellent in reliability was satisfied, the transmittance decreased because of increase of back scattering, or the like. If the transmittance was improved, the diffusing characteristic was lowered. Hence, there was a problem that the balance between light transmittance and diffusing characteristic was hardly kept.
An object of the present invention is to develop a diffusion type adhesive layer which is excellent in balance between light transmittance and diffusing characteristic with satisfaction of self-adhesive applicability excellent in reliability and which is adapted for formation of a liquid-crystal display device excellent in visibility such as brightness.
According to the present invention, there are provided: a diffusing adhesive layer comprising a light-transmissible adhesive layer dispersively containing colorless light-transmissible particles so as to exhibit light diffusing characteristic, wherein the light diffusing characteristic of the diffusing adhesive layer is not higher than 10% in terms of a light diffusion factor which is defined as 100xc3x97I30/I10 when I30 is intensity of light transmitted in a direction inclined by 30 degrees relative to a direction of perpendicular transmission of perpendicularly incident light, and I10 is intensity of light transmitted in a direction inclined by 10 degrees relative to the direction of perpendicular transmission of perpendicularly incident light; an optical member, wherein the above-mentioned diffusing adhesive layer is provided on an optical material having at least a polarizing plate or a retarder plate; and a reflection type liquid-crystal display device, wherein the above-mentioned diffusing adhesive layer is provided between a liquid-crystal cell and a polarizing plate.
According to the another aspect of the present invention, there are provided: a diffusing adhesive layer comprising a light-transmissible adhesive layer dispersively containing colorless light-transmissible particles so as to exhibit light diffusing characteristic, wherein the diffusing adhesive layer has a total light transmission factor of not lower than 85% and a direct transmission factor of not higher than 30%; an optical member wherein the above-mentioned diffusing adhesive layer is provided on an optical material having at least a polarizing plate or a retarder plate; and a reflection type liquid-crystal display device wherein the above-mentioned diffusing adhesive layer is provided between a liquid-crystal cell and a polarizing plate.
According to the present invention, there can be obtained a light diffusion type adhesive layer excellent in balance between light transmittance and diffusing characteristic on the basis of the aforementioned light diffusion factor and applicable to a self-adhesive process with good reliability. A liquid-crystal display device excellent in visibility such as brightness, especially, a reflection type liquid-crystal display device excellent in frontal brightness, can be also obtained by use of the light diffusion type adhesive layer.
According to the present invention, it is possible to obtain a liquid-crystal display device which is excellent in balance between transmitting and diffusing characteristic on the basis of the aforementioned light transmission factor and which is excellent in visibility such as brightness. Especially, it is possible to obtain a reflection type liquid-crystal display device excellent in frontal brightness. Moreover, it is possible to obtain a light diffusing adhesive layer which is applicable to a self-adhesive process with good reliability.
Further it is possible to avoid the necessity of separate provision of a light diffusing plate because the adhesive layer serves also as a light-diffusing layer, the necessity of arranging a light diffusing plate provided separately can be avoided. Hence, it is possible to achieve the reduction in size and weight by omission of members of the liquid-crystal display device.